It is known that automobile headlamps operate in a hot environment within a contained space defined within a headlamp cavity, where air may be constrained between a cover lens and a lamp reflector in which a heat-generating, e.g. incandescent, lamp capsule is mounted. Lamp reflectors are often made of metallized plastics that must withstand elevated temperature, and lamp capsules are made with bases made of heat-resistant plastics, because it is known that in operation an incandescent, e.g. halogen, lamp can reach temperatures of 240 degrees C., as known in column 3 of U.S. Pat. No. 4,609,977 (Eckhardt), which is incorporated by reference in its entirety as if fully set forth herein. Certain plastics used in the headlamp system may degrade due to elevated temperatures. Degraded plastics may cause outgassing which can disadvantageously result in a haze of plastics material being deposited on the reflector optical surface or the front lens, thereby decreasing headlamp efficiency. In operation, it is desired to maintain a temperature, as measured on the lamp capsule bulb wall radially above the filament and corresponding to the capsule's hot spot, not in excess of a maximum temperature of 650 degrees C. It is advantageous to promote a cooling airflow to the reflector cavity.
Simply adding vents in the reflector surface would impair photometric performance. It has been proposed to provide cooling holes in headlamp reflectors, but these disadvantageously put holes in the optical surface and could reduce optical efficiency, see U.S. Pat. No. 6,071,000 (Rapp) and U.S. Pat. No. 5,406,467 (Hashemi). Other proposals add forced air fans rather than passive cooling, adding to component cost, complexity and electrical power load, see U.S. Pat. No. 7,427,152 (Erion) or European Specification EP 1 437 546 (Nolte). Another ventilation proposal is to guide air above the lamp base through the lamp hole which receives the capsule in the reflector, see U.S. Pat. No. 5,457,616 (Grigorescu), requiring a specially modified reflector rear with standoff skirts (22, 24, 26) that, in cooperation with a special cover adaptor (30) clipped to the reflector rear and which holds the lamp capsule, define a radially oriented, planar, sinuous labyrinthine pathway (FIG. 2) intended to pass air but block water, the pathway located axially forward of, and separated from, both the capsule retaining collar (30e, 30f) and the capsule seal gasket (12).
Conventional headlamp capsules, illustrated in U.S. Pat. No. 6,080,019 (Coushaine), U.S. Pat. No. 7,261,451 (Coushaine), and U.S. Pat. No. 5,855,430 (Coushaine) of the present Applicant's assignee, are known, and are each incorporated here in their entirety as if fully set forth herein. Commercial embodiments of such headlamp capsules as seen at Coushaine Pat. '019 at FIGS. 1-5 are generally designated in the trade as, for example SAE type 9005 or 9006 capsules (also known as HB3 and HB4, respectively), which are generally L-shaped, and embodiments of FIGS. 6-12 (or at Coushaine Pat. '430 at FIG. 4) are generally designated in the trade as, for example SAE type 9008 (or H13), which are generally straight.
Other conventional capsule arrangements with a replaceable capsule sealed into a receiving region of a headlamp reflector are known in e.g. U.S. Pat. No. 9,151,459 (Wilson); U.S. Pat. No. 6,082,883 (Tatsumi); U.S. Pat. No. 4,862,337 (Ohshio); and Pub. US 2014/0085921 (Petker), and are understood to suffer thermal disadvantages of the prior art.